[unreadable] Intimal hyperplasia (IH), a disease process that accounts for tremendous morbidity and mortality in patients previously treated with angioplasty or vascular reconstruction, is typified by dedifferentiated vascular smooth muscle cells (VSMC) that proliferate, migrate, and are resistant to apoptosis. In preliminary studies, we found that a subtype of protein kinase C, PKC delta (PKCd), profoundly regulates VSMCs in vitro. Specifically, PKCd inhibits SMC proliferation and migration and stimulates SMC apoptosis and differentiation. Moreover, we found that rapamycin, which inhibits restenosis when applied via coronary stents, increases PKCd in cultured VSMCs, suggesting PKCd may be the signal through which rapamycin exerts its profound inhibitory effect. Based on the foregoing, we propose that the potent effects of PKCd on VSMCs might allow this molecule, or a modification, to be used as a specific preventative therapy. We will begin with studies to define the pathways through which PKCd affects VSMC proliferation, apoptosis, and migration and confirm our preliminary data showing downstream regulation through ERK1, p38 and p53. In specific aim II, we will dissect the PKCd molecule to understand the regulatory mechanism that governs its effects in VSMCs. Specifically; we will evaluate the ability of the catalytic or regulatory domain, as well as phosphorylation of specific tyrosine residues, to regulate PKCd's control over proliferation, migration and apoptosis. In specific aim III, we will test the role of PKCd through three distinct molecular manipulations in rat and mouse arterial injury models. Finally, in aim IV, we will test the hypothesis, both in vivo and in vitro, that rapamycin affects SMC behavior and IH through induction of PKCd. We anticipate that these studies will further our knowledge of the mechanisms and pathways that contribute to the formation of IH. Moreover, we are encouraged by the profound effect that PKCd has on the SMC dysfunction that accompanies IH and postulate that upregulation of this molecule will be a potential strategy for the prevention of this devastating condition. [unreadable] [unreadable]